Technical Field
The present invention relates to antenna devices, and, more particularly, to on-chip antenna structures and methods of manufacturing on-chip antenna structures.
Description of the Related Art
Antennas for devices that employ wireless communication have traditionally been formed off-chip and subsequently coupled to an integrated circuit. However, as the size of communication devices have been scaled down over the years, there has been an increasing demand for more compact antenna structures. While specialized board technologies may be used to fabricate antennas therein, they are often unsuitable for certain applications. For example, for devices that employ frequencies of 60 GHz or higher, the design of antenna into specialized board technologies are quit challenging, as the tolerances of the board technologies are several orders of magnitude higher than microelectronic technologies. Transmitting the millimeter wave signal outside of the chip up to the antenna presents another significant challenge. Thus, one popular means of fabricating antenna devices integrates the antenna on-chip into microelectronic silicon structures.
The current state of the art of integrating antenna into a microelectronic silicon technology, for both RF and mm wave frequencies, provides structures that have a relatively low efficiency due to the loss of transmissions into a lossy silicon substrate and due to the fact that the antenna ground cannot be placed at a sufficient distance away from the antenna. For example, microelectronic silicon structures provide a limited distance (less than 15 μm) between the last layer of metal in which the antenna is situated and the first layer of metal where the ground plane is integrated. As such, state of the art on-chip antennas exhibit lower efficiency and provide a narrower bandwidth than antennas designed into specialized technologies. Further, their product applications are very limited.